*{
    margin: 0;
    padding: 0;
    list-style: none;
}
html,body{
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
}

/* 开始游戏界面 */
.plane{
    width: 100%;
    height: 100%;
    max-width: 420px;
    max-height: 680px;
    background: url(../images/开始背景.png) no-repeat 0 0/100% 100%;
    position: relative;
    overflow: hidden;
}

/* 开始游戏按钮 */
.begin{
    width: 140px;
    height: 50px;
    border-radius: 16px;
    border: none;
    border-bottom: 4px solid #666;
    position: absolute;
    left: calc(50% - 70px);
    bottom: 30px;
    outline: none;
}

.begin:active{
    height: 47px;
    border: 0;
}

.game{
    width: 100%;
    height: 100%;
    background-color: black;
    position: absolute;
    left: 0;
    top: 0;
    z-index: 9;
    display: none;
}

.bg{
    width: 100%;
    height: 100%;
    position: absolute;
    left: 0;
    top: 0;
    background: url(../images/background_1.png) no-repeat 0 0/100% 100%;
}

.bg2{
    /* top: -680px; */
}

/* 我方飞机 */
.myplane{
    width: 48px;
    height: 58px;
    background: url(../images/我的飞机.gif) no-repeat 0 0/100% 100%;
    position: absolute;
    left: calc(50% - 30px);
    top: 600px;
}

img{
    position: absolute;
    z-index: 99;
}